I've developed a program reading and writing serial data using USART6 and pins 6 & 7 on GPIOC. It uses DMA to perform the RX & TX and is working fine. We thought we might be able to save some wiring effort if we could use the ST-Link serial port on the USB so I changed USART6 to USART3 and the tx rx pins to 8/9 on GPIOD. I also changed the baud rate way down to 9600 for testing.
Unfortunately this "simple" change did not work. When I send a serial command to the ST-Link serial port, the program has a catastrophic failure and ends in an exception. The transmit and receive callbacks are never fired.
Is there some limitation on the use of the ST-Link serial channel that prevents this? Also, the failure occurs whether the debugger is running or not.
Thanks for any insight here.